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The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Petriella Zotov

~ Ehrharta

Habit, vegetative morphology. Perennial; rhizomatous. Culms 1–40 cm high; woody and persistent, or herbaceous; unbranched above (but branching near the base). Culm nodes glabrous. Plants unarmed. Young shoots intravaginal. Leaves not basally aggregated; auriculate. Leaf blades linear-lanceolate to ovate-lanceolate; narrow; 2–3 mm wide; flat, or folded; not pseudopetiolate; without cross venation; disarticulating from the sheaths (from the lower sheaths), or persistent. Ligule a fringed membrane; not truncate; to 0.5 mm long. Contra-ligule absent.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.

Inflorescence. Inflorescence a single raceme, or paniculate; contracted; espatheate; not comprising ‘partial inflorescences’ and foliar organs. Spikelet-bearing axes persistent. Spikelets solitary; not secund; pedicellate; imbricate.

Female-fertile spikelets. Spikelets 3–5 mm long; compressed laterally; disarticulating above the glumes; with conventional internode spacings. Rachilla terminated by a female-fertile floret. Callus absent.

Glumes present; two; more or less equal; shorter than the spikelets; shorter than the adjacent lemmas (2.0–3.5 mm long); hairless; glabrous; pointed, or not pointed; awnless; carinate; very dissimilar, or similar (G1 or G2 may be rounded, truncate or acute at the tip). Lower glume shorter than the lowest lemma; much shorter than half length of lowest lemma; 1–3 nerved. Upper glume 3–5 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 2 (the lemmas glabrous except at the base, without basal appendages, with prominent longitudinal veins but without transverse ribs); epaleate; sterile. The proximal lemmas awned (the apex acuminate, contracted into a short terminal awn); 0–7 nerved; more or less equalling the female-fertile lemmas to decidedly exceeding the female-fertile lemmas; decidedly firmer than the female-fertile lemmas; not becoming indurated.

Female-fertile florets 1. Lemmas decidedly firmer than the glumes (chartaceous); not becoming indurated; entire; blunt (truncate); awnless; hairless; glabrous; carinate; without a germination flap; 1–5 nerved. Palea present; relatively long (3/4 the length of the lemma); entire; awnless, without apical setae; thinner than the lemma (hyaline-membranous); not indurated; 1-nerved (i.e. the two veins contiguous); one-keeled. Lodicules present; 2; free; membranous; glabrous; at least slightly toothed; relatively heavily vascularized (cf. Ehrharta). Stamens 2. Anthers 1–1.5 mm long; without an apically prolonged connective. Ovary apically glabrous. Styles free to their bases. Stigmas 2; white.

Fruit, embryo and seedling. Fruit free from both lemma and palea; small (2–3.5 mm long); ellipsoid; strongly compressed laterally. Hilum long-linear. Embryo small.

Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Ehrharteae. Soreng et al. (2015): cf. Oryzoideae (as a synonym?); Ehharteae. 2 species.

Distribution, phytogeography, ecology. New Zealand.

Helophytic to mesophytic; species of open habitats; glycophytic. Mountains.

Special comments. Seems scarcely distinguishable from Ehrharta and Tetrarrhena. Anatomical data wanting. Illustrations. • P. colensoi, as Ehrharta: Cheeseman (1914), Ill. New Zealand Flora, 2

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 11th December 2017.’.